Abstract

To improve driving safety on superhighways, longitudinal profile design parameters of a superhighway are calculated via force analysis while a car is driven on a slope. The calculations consider characteristics of drivers, cars, and roads. According to the vehicle type, design speed, and natural conditions, the maximum longitudinal slope of a superhighway is calculated and compared with those of an ordinary superhighway and high-speed railway. Based on analysis of the vehicle climbing performance, braking performance, and driver visual characteristics, the maximum and minimum slope lengths of a superhighway are calculated. By analyzing the elements of vertical curves, the minimum radius and minimum length of the vertical curves of a superhighway are calculated by considering factors such as mitigating the impact at the slope bottom, driving at night, and driving time along vertical curves. Analysis and calculation results show that when the maximum longitudinal slope is 2.50%, 2.25%, and 2.00%, the minimum slope length is 450 m, 400 m, and 350 m, respectively, and the minimum vertical curve length is 145 m, 130 m, and 115 m, respectively, and the superhighway travel requirements can be satisfied at speeds of 180 km/h, 160 km/h, and 140 km/h, respectively.

Highlights

  • IntroductionIn more than 10 countries in Europe, such as France and the Netherlands, the maximum speed limit on highways is 130 km/h [1], and in Texas, USA, the maximum speed limit is 137 km/h (85 mile/h) [2]; in Italy, it is 140 km/h [3], while in Germany, there is no maximum speed limit on some highways [4]. e Highway Engineering Design Guidelines (Draft) published in 1951 stipulated for the first time that the maximum design speed of highways in China was 120 km/h, and it has been used ever since [5]

  • The longitudinal profile of superhighways was not considered in these studies. erefore, based on force analysis while operating a vehicle on a slope, in this paper, the maximum longitudinal slope of superhighways is calculated according to the vehicle type, design speed, and natural conditions and compared with the maximum longitudinal slopes of ordinary highways and high-speed railways; based on analysis of the vehicle braking performance and driver visual characteristics, the maximum and minimum slope lengths of superhighways are obtained; based on analysis of elements of vertical curves, the minimum radius and minimum length of vertical curves of superhighways are calculated, taking into account factors such as mitigating the impact, illuminated distance, sight distance, and driving time along vertical curves

  • E investigation method is aimed at determining the maximum longitudinal slope value by investigating the driving conditions of automobiles on slopes and analyzing survey data of slope sections. e test method selects the design vehicle as the experimental object, drives on different longitudinal slopes at different speeds, and determines the appropriate longitudinal slope according to the parameters of the vehicle speed and slope length of the designed route

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Summary

Introduction

In more than 10 countries in Europe, such as France and the Netherlands, the maximum speed limit on highways is 130 km/h [1], and in Texas, USA, the maximum speed limit is 137 km/h (85 mile/h) [2]; in Italy, it is 140 km/h [3], while in Germany, there is no maximum speed limit on some highways [4]. e Highway Engineering Design Guidelines (Draft) published in 1951 stipulated for the first time that the maximum design speed of highways in China was 120 km/h, and it has been used ever since [5]. Considering that the speed limit on highways in many countries exceeds 120 km/h, automobile and highway construction technologies in China have attained great progress, and the concept of a superhighway was proposed for the first time by the current authors. Erefore, based on force analysis while operating a vehicle on a slope, in this paper, the maximum longitudinal slope of superhighways is calculated according to the vehicle type, design speed, and natural conditions and compared with the maximum longitudinal slopes of ordinary highways and high-speed railways; based on analysis of the vehicle braking performance and driver visual characteristics, the maximum and minimum slope lengths of superhighways are obtained; based on analysis of elements of vertical curves, the minimum radius and minimum length of vertical curves of superhighways are calculated, taking into account factors such as mitigating the impact, illuminated distance, sight distance, and driving time along vertical curves The longitudinal profile of superhighways was not considered in these studies. erefore, based on force analysis while operating a vehicle on a slope, in this paper, the maximum longitudinal slope of superhighways is calculated according to the vehicle type, design speed, and natural conditions and compared with the maximum longitudinal slopes of ordinary highways and high-speed railways; based on analysis of the vehicle braking performance and driver visual characteristics, the maximum and minimum slope lengths of superhighways are obtained; based on analysis of elements of vertical curves, the minimum radius and minimum length of vertical curves of superhighways are calculated, taking into account factors such as mitigating the impact, illuminated distance, sight distance, and driving time along vertical curves

Overview of Superhighways
Analysis of Vehicle Driving Force
Maximum Longitudinal Slope of a Superhighway
Minimum Longitudinal Slope of a Superhighway
Slope Length Limit of a Superhighway
Vertical Curves of Superhighways
Findings
Conclusion

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